title: Recent warming by latitude associated with increased length of ragweed pollen season in central North America.
abstract: A fundamental aspect of climate change is the potential shifts in flowering phenology and pollen initiation associated with milder winters and warmer seasonal air temperature. Earlier floral anthesis has been suggested, in turn, to have a role in human disease by increasing time of exposure to pollen that causes allergic rhinitis and related asthma. However, earlier floral initiation does not necessarily alter the temporal duration of the pollen season, and, to date, no consistent continental trend in pollen season length has been demonstrated. Here we report that duration of the ragweed (Ambrosia spp.) pollen season has been increasing in recent decades as a function of latitude in North America. Latitudinal effects on increasing season length were associated primarily with a delay in first frost of the fall season and lengthening of the frost free period. Overall, these data indicate a significant increase in the length of the ragweed pollen season by as much as 13-27 d at latitudes above ~44°N since 1995. This is consistent with recent Intergovernmental Panel on Climate Change projections regarding enhanced warming as a function of latitude. If similar warming trends accompany long-term climate change, greater exposure times to seasonal allergens may occur with subsequent effects on public health.
authors.affiliation: Crop Systems and Global Change Laboratory, Agricultural Research Service, United States Department of Agriculture, Beltsville, MD 20705, USA. l.ziska@ars.usda.gov
authors.forename: Lewis
authors.initials: L
authors.lastname: Ziska
authors.forename: Kim
authors.initials: K
authors.lastname: Knowlton
authors.forename: Christine
authors.initials: C
authors.lastname: Rogers
authors.forename: Dan
authors.initials: D
authors.lastname: Dalan
authors.forename: Nicole
authors.initials: N
authors.lastname: Tierney
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Elder
authors.forename: Warren
authors.initials: W
authors.lastname: Filley
authors.forename: Jeanne
authors.initials: J
authors.lastname: Shropshire
authors.forename: Linda B
authors.initials: LB
authors.lastname: Ford
authors.forename: Curtis
authors.initials: C
authors.lastname: Hedberg
authors.forename: Pamela
authors.initials: P
authors.lastname: Fleetwood
authors.forename: Kim T
authors.initials: KT
authors.lastname: Hovanky
authors.forename: Tony
authors.initials: T
authors.lastname: Kavanaugh
authors.forename: George
authors.initials: G
authors.lastname: Fulford
authors.forename: Rose F
authors.initials: RF
authors.lastname: Vrtis
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Patz
authors.forename: Jay
authors.initials: J
authors.lastname: Portnoy
authors.forename: Frances
authors.initials: F
authors.lastname: Coates
authors.forename: Leonard
authors.initials: L
authors.lastname: Bielory
authors.forename: David
authors.initials: D
authors.lastname: Frenz
mesh_terms: D031164:Ambrosia; D001249:Asthma / Q000209:etiology; D002980:Climate; D006801:Humans; D009656:North America; D011058:Pollen; D006255:Rhinitis, Allergic, Seasonal / Q000209:etiology; D012621:Seasons; D013696:Temperature